Crossreactivity between Dermatophagoides siboney and other house dust mite allergens in sensitized asthmatic patients

Subcutaneous allergen immunotherapy for asthma: A randomized, double-blind, placebo-controlled study with a standardized Blomia tropicalis vaccine

BACKGROUND

Sensitization to Blomia tropicalis (Bt) is very frequent in the tropics, and particularly in Cuba, being a significant cause of allergic asthma. Allergen immunotherapy (AIT) with Bt can be a therapeutic option, however, placebo-controlled clinical trials have not been reported.

OBJECTIVE

To assess the therapeutic effect and safety of AIT for asthma using a standardized allergen vaccine of B. tropicalis by subcutaneous route, in allergic asthmatic patients exposed and sensitized to this mite species.

METHODS

A double-blind, placebo-controlled Phase II trial was conducted in 35 adults (18 with treatment and 17 with placebo), with mild to moderate asthma, predominantly sensitized to Bt. AIT was administered subcutaneously in increasing doses from 4 to 6000 Biological Units using a locally manufactured standardized extract (BIOCEN, Cuba). Patient assessment was performed using symptom-medication score (SMS), peak expiratory flow and skin reactivity relative to Histamine as measured by skin prick test (SPT).

RESULTS

The 12-month treatment achieved a significant (p < 0.001) decrease of SMS. Symptom score showed only 41% (CI: 26-61) of placebo values, whereas medication was 34.5% (22.4%-63.3%). Treatment was regarded clinically effective in 67% of patients (OR 32; 95%CI: 17 to 102). The effect size on symptoms and medication was higher than has been reported with equivalent allergen dosages of D. pteronyssinus and D. siboney in Cuban asthmatic patients. Skin reactivity to Bt was also significantly reduced (p = 0.0001), increasing 148-fold the allergen threshold to elicit a positive skin test. This desensitization effect was specific to Bt and did not modify the reactivity to Dermatophagoides. The change of specific skin reactivity was significantly (p < 0.05) correlated to clinical improvement. All adverse events were local with a frequency of 2.4% of injections.

CONCLUSIONS

Subcutaneous AIT with Blomia tropicalis was effective and safe in asthmatic adults exposed and sensitized to this mite species in a tropical environment.

TRIAL REGISTRATION

Cuban Public Registry of Clinical Trials: RPCEC00000026 (WHO International Clinical Trial Registry Platform ICTRP).

Mite and booklouse fauna from vacuumed dust samples from beijing

A significant-source of allergens come from house dust that contain particles derived from arthropods, molds, and pet dander. This study evaluated mite and booklouse fauna from vacuumed dust samples in Beijing China (a temperate zone). Our survey was carried out in Beijing in the homes of mite allergic patients who visited our Allergy Department. In total, 38 homes were selected for the collection of dust samples by vacuuming, from December 2008 to January 2010. The flotation method was used to isolate mites from house dust. Permanent slides were prepared for mite specimens and mites were identified and counted under a microscope. In total, 1,798 separate mite and insect specimens were found in 345 dust samples taken from 38 homes. A total of 95 individual Dermatophagoides (D) siboney were detected in 35 dust samples from 19 homes (representing 5.3% of all mite and insect species found in house dust); in addition, this mite was found to co-exist with D. farinae (Hughes, 1961) in 33 dust samples. Our results demonstrated the presence D. siboney that co-existed with D. farinae in house dust in Beijing China (a temperate zone).

Correlation between skin tests to Dermatophagoides pteronyssinus, Dermatophagoides siboney and Blomia tropicalis in Cuban asthmatics

BACKGROUND

Dermatophagoides pteronyssinus, Dermatophagoides siboney and Blomia tropicalis are the most important allergenic mites in Cuba. The aim of this study was to determine the degree of polysensitization and correlation of the skin prick test (SPT) reaction size to these mites in asthmatic patients.

METHODS

A total of 232 adult patients with asthmatic symptoms caused by house dust and positive SPT to at least one mite were included. Standardized allergenic extracts were used in SPT.

RESULTS

A total of 88.4% of patients were positive to D. siboney, 87.1% to D. pteronyssinus, and 68.1% to B. tropicalis. Sensitization to Dermatophagoides species was predominant, demonstrated by the fact that 31.9% of patients showed positive SPT to either D. siboney or D. pteronyssinus only, whereas only 5.6% was sensitized solely to B. tropicalis. Nevertheless, most patients (58.6%) were polysensitized to the 3 species. The mean wheal size produced by the different allergens in positive patients was similar (n.s. p > 0.05). Reaction size was strongly correlated (r = 0.71, p = 5.3 x 10-09) between D. siboney and D. pteronyssinus, whereas no significant correlation was found between D. pteronyssinus or D. siboney and B. tropicalis.

CONCLUSIONS

The results of this study support the need to include the 3 allergens in diagnostic panels and for combined allergen-specific immunotherapy.

Immunoglobulin E reactivity of native Blo t 5, a major allergen of Blomia tropicalis

BACKGROUND

Blo t 5 is a major allergen of Blomia tropicalis and its complementary DNA (cDNA) has been expressed in both prokaryotic and eukaryotic expression systems. Although the recombinant Blo t 5 has been well characterized, relatively less is known about its native counterparts and the allergenicity comparison of the native and recombinant Blo t 5 allergens has not been reported.

OBJECTIVE

The aims of this study are to characterize the native counterpart of Blo t 5, and compare the allergenicity of native and recombinant Blo t 5 by in vivo and in vitro assays.

METHODS

Native Blo t 5 were purified by immuno-affinity chromatography and characterized by proteomic means. The allergenicity of the allergen was evaluated by skin prick tests, human IgE ELISA, ELISA inhibition and histamine release assays.

RESULTS

Native Blo t 5 consists of at least five distinct isoforms, ranging from pI 3 to 5.5. Allergenicity assessment of recombinant and native Blo t 5 based on skin reaction, IgE-binding capacity and histamine release in allergic individuals indicated that there was a good correlation between both forms of Blo t 5 in general. However, data from IgE ELISA inhibition assay revealed the presence of additional unique IgE epitopes in native Blo t 5.

CONCLUSIONS

At least five distinct isoforms of Blo t 5 have been identified. Comparative assessment of native and recombinant Blo t 5 revealed that the allergenicity of these two forms was similar but not completely identical suggesting that the various isoforms of native Blo t 5 may exhibit additional unique IgE epitopes.

Skin test reactivity to natural and recombinant Blomia and Dermatophagoides spp. allergens among mite allergic patients in the UK

BACKGROUND

Many asthmatics in tropical and subtropical areas have positive skin prick tests to both Dermatophagoides spp. and to the mite Blomia tropicalis. This may be due to recognition by IgE of cross-reactive allergens between the different mite species or because of sensitization to species-specific allergens. A 14-kDa Blomia tropicalis allergen, Blo t 5, has been cloned and shows 40% sequence homology with Der p 5. The aim of this study was to investigate reactivity to B. tropicalis in patients known to be sensitized to D. pteronyssinus and to assess allergenic activity and cross-reactivity of recombinant (r) Group 5 allergens amongst these patients, who live in the UK and who are not exposed to B. tropicalis in their homes.

METHODS

Patients (n = 19) with asthma and/or rhinitis were selected based on clinical history and a positive skin prick test to D. pteronyssinus extract and were compared with non-allergic skin test negative controls (n = 10). IgE antibody responses to Blomia tropicalis, Dermatophagoides pteronyssinus, rDer p 5 and rBlo t 5 were compared by quantitative intradermal skin testing using serial 10-fold dilutions of each allergen. End point titre was the highest dilution giving an 8 x 8 mm wheal at 15 min. IgE antibodies to Blomia tropicalis, Dermatophagoides pteronyssinus, rDer p 5 and rBlo t 5 were measured using RAST, CAP and RIA, respectively.

RESULTS

All 19 patients had positive skin tests to D. pteronyssinus at concentrations of 0.001 to 1 AU/ml and 10 were skin test positive to rDer p 5 at concentrations of 10-4 to 5 micro g/ml. Positive intradermal tests to Blomia tropicalis were seen in 12/19 patients at concentrations of 0.002 to 2 micro g/ml. However none of the patients had positive skin tests to rBlo t 5. Non-allergic controls were all skin test negative at the highest concentration of each allergen tested. All subjects had quantifiable specific IgE to D. pteronyssinus, but only two had IgE to B. tropicalis. IgE to Der p 5 was found in six patients, but no patients had IgE to Blo t 5.

CONCLUSIONS

This study of patients naturally exposed to D. pteronyssinus but not to Blomia tropicalis, provides evidence for IgE mediated cross-reactivity between allergens produced by both mite species. The results suggest that the Group 5 allergens of D. pteronyssinus and B. tropicalis are species-specific.

Arthropod allergens and human health

Many species of arthropods are the sources of potent allergens that sensitize and induce IgE-mediated allergic reactions in humans. Most of these arthropod allergens are proteins, and the allergic response mechanism to these allergens is the same as it is for allergens from other sources such as plant pollens, molds, and foods. Aside from ingestion of crustaceans (shrimp, lobster), among arthropods, humans have the greatest contact with insects and mites, and as a result allergies to these two groups of arthropods have been the most frequently reported. Because of the large number of people affected by allergic reactions to stinging insects, cockroaches, and dust mites, many allergens of these organisms have been extensively studied, purified, and immunobiochemically characterized and for some recombinant allergens, produced. Cocktails of these recombinant allergens have the potential for use in diagnosis and immunotherapy. In this chapter, we review the insects and mites that induce allergic reactions. Where the information exists, the immunobiochemical characterization of the allergens and the frequency of sensitivity or clinical reactivity in the human population are also reviewed. As background, the beginning of this review includes sections that define allergens, explain the allergic reaction mechanism, and describe the methods for naming allergens.

Cross-reactivity of Tyrophagus putrescentiae with Dermatophagoides farinae and Dermatophagoides pteronyssinus in urban areas

BACKGROUND

Tyrophagus putrescentiae (TP) have cohabited with D. pteronys-sinus (DP) and D. farinae (DF) in more than 25% of houses in urban areas of Korea, and many atopic subjects have also been cosensitized to TP and Dermatophagoides species.

OBJECTIVE

We evaluated the cross-reactivity of TP with DF and DP in atopic subjects of urban inhabitants.

METHODS

The cross-reactivity was evaluated with inhibition ELISA and immunoblotting. Allergenic components of TP were evaluated with IgE immunoblotting of the sera from 25 individual atopics. All enrolled subjects lived in urban areas.

RESULTS

In ELISA inhibition with pooled sera, all TP, DP, and DF extract inhibited TP-specific IgE by more than 90%, and the 50% inhibitory concentrations of TP, DP, and DF extract were 0.4 microg/mL, 0.8 microg/mL and 0.8 microg/mL, respectively. The maximum inhibition, however, of DP-specific and DF-specific IgE by TP extracts was 32% and 29%, respectively. With six individual sera, the TP-specific IgE was also inhibited by more than 88% with DF extract in all cases. In inhibition immunoblotting, all of the TP, DP, and DF extracts completely inhibited the TP-specific IgE bands at a concentration of 2.0 microg/mL. Fifteen allergenic components in TP were found. Among them, the 16-kD allergen was most prevalent (52%) and its IgE binding was completely inhibited by 0.1 microg/mL of purified Der f2 and it also bound with 2 different monoclonal antibodies to the group 2 allergen of Dermatophagoides species.

CONCLUSIONS

Our results suggested considerable cross-reactivity between TP and the two Dermatophagoides species in urban areas where TP and Dermatophagoides species cohabit. The 16-kD allergen, which shared common epitopes with the group 2 allergen of Dermatophagoides, is one of the most prevalent allergens of TP.

Sensitization to local dust-mite fauna in Singapore

BACKGROUND

Recent studies showed the presence of a unique dust-mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens.

METHODS

The skin prick test was performed on a total of 391 individuals (289 patients with asthma and/or allergic rhinitis and 102 healthy controls) using extracts of six species of local dust mites (Austroglycyphagus malaysiensis, Blomia tropicalis, Dermatophagoides pteronyssinus, D. farinae, Sturnophagoides brasiliensis, and Tyrophagus putrescentiae) and 10 other common indoor allergens. Total serum IgE and specific IgE to these dust mites were also quantified with the fluorescence allergosorbent test (FAST).

RESULTS

The sensitization rates among patients with asthma and/or allergic rhinitis to dust mites and other inhalant allergens tested (via skin prick tests) were as follow: B. tropicalis (96.2%), D. pteronyssinus (93.4%), D. farinae (92.3%), A. malaysiensis (78.2%), S. brasiliensis (71.6%), T. putrescentiae (71.3%), canary feathers (69.9%), Periplaneta americana (cockroach) (59.5%), Blattella germanica (cockroach) (56.4%), mosquito (Aedes sp.) (46.4%), dog epithelia (mixed breed) (34.3%), kapok seed (31.8%), cat hair (29.1%), Aspergillus fumigatus (20.8%), Penicillium notatum (18.0%), and Candida (Monilia) albicans (9.3%). All patients were observed to react to at least three of the six dust-mite extracts, with 254/289 (87.9%) reacting to at least five or to all six. Skin prick responses to the dust mites were found to correlate with the corresponding specific IgE levels quantified by FAST (P<0.001). In addition, specific IgE levels to D. pteronyssinus and D. farinae were highly correlated (Spearman's rank coefficient = 0.76, P<0.001), as were those to B. tropicalis and A. malaysiensis (r = 0.60, P<0.001).

CONCLUSIONS

Asthma and/or allergic rhinitis patients were highly sensitized to the local dust-mite fauna. Thus, these dust mites should be considered important allergenic sources of this region.

Allergenic differences between the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus

BACKGROUND

House dust mite allergens are the most important indoor allergens associated with asthma and rhinitis in Singapore and the tropics. Recent data to suggest that besides the Dermatophagoides spp., the domestic mite Blomia tropicalis (Bt) is also an important source of allergens in these regions.

OBJECTIVE

To evaluate the degree of allergenic cross-reactivity between Bt and D. pteronyssinus (Dp).

METHODS

Cross-reactivity between extracts of Bt and Dp was evaluated by fluorescent allergosorbent (FAST) inhibition studies and cross enzyme immunoelectrophoresis. Additionally, the major Dp allergens - Der p 1, Der p 2 and Der p 5, were also compared with the Bt extract by dot blot inhibition. Skin prick and intradermal end-point titration were then carried out to compare the homologous allergens of the mite species, Blo t 5 and Der p 5.

RESULTS

FAST inhibition studies showed low to moderate cross-reactivity between the two dust mite extracts (maximum cross-inhibition, 60%). Native allergens studied by cross enzyme immunoelectrophoresis using mite allergic sera also showed similar results but with at least four cross-reactive IgE binding antigens. Dot blot inhibition studies using allergens of Dp, Der p 1, Der p 2, and Der p 5, showed little cross-reactivity between these allergens with components of the crude Bt extracts. Further, evaluation of a recombinant allergen of Bt, Blo t 5, showed low levels of cross-reactivity even with its homologous Dp counterpart, Der p 5.

CONCLUSION

These results provide evidence that Bt allergens are distinct and have relatively low to moderate cross-reactivity with Dermatophagoides spp. allergens. Bt allergens should therefore be included in the diagnostic panel for the evaluation of allergic disorders in the tropics, and the development of new diagnostic and therapeutic strategies should include allergens of Bt.

Biologic activity of Dermatophagoides siboney and Blomia tropicalis allergens in exposed and unexposed mite-allergic individuals. Effect of patient selection on the biologic standardization of mite extracts

BACKGROUND

This study aimed to investigate the influence of patient selection criteria, i.e., mite-allergic individuals exposed and not exposed to Dermatophagoides siboney and Blomia tropicalis, on the biologic activity of mite extracts. Determination of the potency of mite extracts in vivo requires selection of patients with a clinical history of mite allergy. In Scandinavia, there are some anamnestic criteria for mite allergy, whereas in the tropics, where patients are continuously exposed to high levels of mites, selection of patients with mite allergy by clinical history is difficult.

METHODS

A total of 210 Cuban asthmatics with continuous symptoms, and 43 Swedes with a clinical history of mite allergy were investigated. Skin prick tests were performed with D. siboney, D. pteronyssinus, D. farinae, B. tropicalis, Acarus siro, Lepidoglyphus destructor, and Tyrophagus putrescentiae extracts. For analysis of the biologic activity of mite extracts, Cuban patients were divided into four groups: 1) all patients skin-test-positive to mites 2) patients positive to mites, but not to other inhalant allergens 3) patients reacting most to the mite species analyzed 4) patients reactive only to mites and reacting most to the mite species analyzed. The biologic potency was calculated according to the Nordic Guidelines.

RESULTS

Due to cross-reactivity between mites, Swedish mite-sensitive patients, with a clear clinical history of mite allergy, but not exposed to D. siboney and B. tropicalis, were more skin reactive to these mites than were Cubans. The estimated potency increased gradually to >200% in group 4. In group 1 Cubans, the reactivity to all mites but B. tropicalis was lower than that in mite-sensitive Swedes.

CONCLUSIONS

According to the influence of patient selection criteria on the estimation of the potency of mite extracts, the determination of the biologic activity of allergenic extracts in subjects without a clear-cut clinical history should be replaced by new methods when available.

Guanine, mite, and cockroach allergens in Costa Rican homes

Previous studies of schoolchildren in Costa Rica have shown an asthma prevalence of 23% and a high level of sensitization, particularly to mite allergens. As a continuation of these studies, some 400 dust samples were collected from various places in Costa Rica, and parts of these were analyzed for specific mite and cockroach allergens, as well as for the number of mites and amount of guanine. Guanine was quantified by a diazo, as well as an HPLC method, which were found to be highly correlated. The concentrations of guanine by the diazo method, Der p 1, Der f 1, and the number of mites were higher in bed dust than in bedroom floor dust, and it was possible to quantify mite allergens and guanine in almost all bed-dust samples. The mean levels were 2-3 times higher than the proposed risk level for elicitation of symptoms in mite-sensitive asthmatics. Bed and bedroom floor dust contained more guanine and mite allergen in humid (> 2000 mm rain) than in drier places (P < 0.05), but the number of mites in bed and bedroom floor dust was higher in less humid places (P = 0.01). The guanine content in bedroom floor dust was higher in areas with a temperate climate than in areas with a warmer climate (P < 0.001, Bartlett's chi square [BCS]), as was the number of mites (P < 0.01, Kruskal-Wallis [KW], 0.04, BCS) and the Der p 1 concentration (P = 0.01, BCS; P = 0.02, KW). The Der f 1 concentration in bedroom floor dust was higher in a warmer than in a temperate climate (P < 0.001, BCS). More guanine and mites were found in urban than in rural bed dust (P = 0.03, KW). Dust samples from the metropolitan area (temperate climate) of Costa Rica contained higher levels of guanine (P < 0.01) and Der p 1 (P = 0.07) than the coastal areas, but very little Der f 1. In these samples, guanine and Der p 1 allergen were closely related, and 2 micrograms of the allergen was equivalent to 0.49 mg of guanine. Two-thirds of bed and floor samples collected on cotton filters contained Bla g 2 allergen at mean levels of 1.6 and 2.1 units/g dust, respectively. Cockroach allergen was, however, absent in all bed samples from the metropolitan area, but did occur in very high concentrations in the coastal bed dust samples collected with tighter polyester filters. In conclusion, the concentration of guanine and Der p 1 was very high in the bed dust of Costa Rican homes. Some factors, such as humidity, small houses for large families, and type of bedding, probably favored the heavy mite infestation, which is probably related to the widespread occurrence of bronchial asthma in this country.

Sensitization to Dermatophagoides siboney, Blomia tropicalis, and other domestic mites in asthmatic patients

Mite species adapted to warm, humid climates are commonly found in house dust in the tropics. In Cuba, Dermatophagoides pteronyssinus, D. siboney, and Blomia tropicalis are the most common and abundant mite species in house dust. To investigate the pattern of sensitization of Cuban asthmatic patients to common mite species, we skin-prick-tested (SPT) 148 patients with a clinical history of asthma and possible mite allergy, and determined specific IgE antibodies against mite allergens (D. pteronyssinus, D. farinae, D. siboney, B. tropicalis, Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Glycyphagus domesticus). The prevalence of positive SPT was high to D. siboney (88%), D. pteronyssinus (87%), A. siro (85%), B. tropicalis (85%), and D. farinae (83%). The largest skin reactions were obtained with D. siboney and B. tropicalis extracts. The skin test response to the D. siboney extract correlated to those of D. farinae, D. pteronyssinus, B. tropicalis, and A. siro. The highest IgE levels were found to Dermatophagoides species and B. tropicalis. IgE to D. siboney and B. tropicalis were found in 97% and 96% of the patients, respectively. The prevalence of specific IgE to the other mites studied varied from 46 to 65%. D. siboney and B. tropicalis are important sensitizers among asthmatic patients in Cuba.